Liquid heater



June 10, 1941. c, c. ABBOTT LIQUID HEATER Filed Aug. 28, 1938 Inventor: Charles C. Abbott 5 W His Attorney- Patented June 10, 1941 LIQUID HEATER Charles 0. Abbott, Pittsfleld, Masa, assignor to General Electric Company, a corporation of New York Application August 28, 1939, Serial No. 292,177

7.0laims. (01. 219-49) My invention relates to new and useful improvements in heaters and more particularly electric liquid heaters such as water heaters,

It is an object of my invention to provide a liquid heater which is of simple and compact construction, which is eflicient in operation, and which may be manufactured at low cost.

' It is a further object of my invention to provide an instantaneous liquid heater constructed and arranged so that the thermal inertia of the heater is reduced to a minimum.

It is a more specific object of my invention to provide a new and improved liquid heater employing a sheathed wire type heating unit the metallic sheath of which cooperates with the other portions of the heater construction to form a spiral path through the heater for the liquid being heated.

Further objects and advantages of my invention will appear as the following description proceeds and the features of novelty which characterize my invention will be more fully set forth in the claims appended to and forming a part of this application.

For a more complete understanding of my invention, reference should be had to the accompanying drawing in which-Fig. 1 is a front sectional elevation of my improved water heater and Fig. 2 is a view partly in section taken on the line 2-2 of Fig. 1.

Referring to the drawing, it will be observed that my improved liquid heater construction comprises a substantially cylindrical outer shell I0 rounded at one end and open at the opposite end. Provided in the rounded end of the outer shell is an outlet sleeve l2 and arranged to cover the open end of the shell is a cap l3 having an inlet opening it. In order to produce a liquidtight construction, the outlet connection l2 and the cap [3 are secured to the shell I!) by a brazed or soldered joint l2a and Na respectively. It will be understood that the inlet opening it will be connected to a cold water supply pipe l5 and the outlet sleeve I2 will be connected to a hot water supply system (not shown) I Provided within the outer shell I0 is a central core member I6 made of copper or brass or some similar good heat conducting material. In order to reduce the mass of this core member and thus reduce the thermal inertia of the heater unit so that the time required to produce hot water when starting from a cold condition is decreased, the core member I6 is made in the form of a hollow cylinder having relatively thin walls. In the preferred form of my invention, the core member I6 is made from two hollow cylindrical members I1 and it closed at one end and hermetically sealed together at their open ends.

Provided within the outer shell I0 is a heating element I! which is in the form of two spirals or a double helix as shown in Fig.1. In forming the heater element it is first bent to a hairpin shape and then both legs of the hairpin are wound simultaneously on a suitable arbor. After forming, the heater element and core member are assembled so that the core member is supported by the heater element.

The spirals of the heating element are formed so that their outside diameters are substantially the same as the inside diameter of the shell Hi and their inside diameters are substantially the same as the outside diameter of the core It. With such a construction and arrangement, the heating element, when located in its operative position between the shell to and the metallic core Ii, engages the inside wall of the outer shell and the outside wall of the core to define a pair of spiral paths which the liquid, in traveling from the inlet H to the outlet l2, must follow thus increasing the length of time the liquid is in contact with the heater element. It is to be observed that with my improved heater construction, the liquid being heated comes in direct contact with the heating element thereby increasing the efliciency of heat transfer between the liquid and the element.

In the preferred form of my invention, the heating element I0 is of the sheathed wire type such as is described and claimed in United States Letters Patent 1,367,341, granted February 1, 1921 on an application filed by myself. Briefly, such a heater element comprises an outer metallic sheath 20 in which a coiled resistance unit 2| is embedded in a compacted mass of powdered heat refractory, electrically insulating material 22, such as magnesium oxide. One characteristic of such a heater unit is that it can be readily formed to the desired spiral shape. It will be understood that the resistance unit 2| has its ends connected to electric terminals 23 and 24 which project from the ends of the sheath 22 and are electrically insulated from the sheath.

As shown in Fig. 1, the cap I3 is provided with a pair of openings 25 and 26 into which the end portions of the heating unit are projected. These openings 25 and 26 communicate with enlarged chambers 21 and 28. The cap l3 serves as a support from which the heating unit is suspended. In effecting this support, the ends of the sheath 22 are projected through the openings 25 and 26 and into the chambers 21 and 28 respectively. The portion of the sheath projecting beyond the end of the openings 25 and 26 is flared outwardly against the shoulders 29 and 80 formed by the increase in diameter of chambers 21 and 28 over the openings 25 and 26. In order to improve the strength of this supporting structure and to provide a leak-proof connection, the heating unit is further secured to the cap it :by brazed joints 3! and 32.

' In order to electrically insulate the terminals 23 and 26 from the cap it, a mass of insulating material 33, such as a. suitable phenolic condensation product, is provided to completely fill each of the chambers 21 and 28. In order to make this joint liquid-tight, the phenolic condensation product is cured after filling as described in Patent 1,770,824, issued July 15, 1930, on an application filed by myself. Each of the chambers is closed by means of a bushing 34 made from some suitable electrically insulating material such as porcelain and a portion 35 which extends into each of the chambers 21! and 28. In order to keep the phenolic condensation product from escaping during the curing operation, which causes it to swell, a copper or other suitable gasket 36 is provided between the head 31 of each bushing and the cap is.

As described in my aforementioned Patent 1,770,824 the bushing 31 will be put 'in place while the material 33 is in a semi-plastic state so that the material is free to flow around the portion 35 and secure the bushing in position upon hardening. Preferably, 'the opening in the bushing through which the terminals 23 and 2d pass will be tapered so that when the bushing is forced into position the material will flow upwardly through the opening about the terminal.

Secured to the end of each terminal 23 and 25 is a connector 38. Preferably 'these connectors ea bea I and liquid is srewhlhte the shell as through,

theinlet id and passes through the shell. inha spiral path being at all times maintained in contact with'either the sheath 22 of the heater element IE or the more it and outer shell it which are heated by the element l9. Since the will be of the tubular type and will be compressed about the ends of the terminals by some suitable swaging operation. Each connector is provided with a clamping member 39 secured to the connector by means of a screw 40.

. A suitable cover M' is provided which is secured to the cap I3 by means of suitable screws Ma and encloses the connectors and clamping members. This cover is provided with an insulating bushing 42 through which conductors may pass to the connectors in order to connect the heater to a suitable source of electrical sup- P y.

In suspending the heater element I9 from the cap l3 it is possible that the unit may sag or lengthen due to the turns of the spiral opening up. This sagging might be suflicient to cause the end of the unit to come into engagement with the outlet sleeve I2 and partially or totally blogck the flow of liquid therethrough. In order.

' the bottom of the shell. In the event that the heater unit sags so that it tends to close the the cap i3 iseconnected to the cold liquid supply system and the outlet sleeve I2 is connected to the hot liquid supply system. Upon a demand for heated liquid, the heater unit i9 is energized thermal inertia of core I0 is low, the temperature of the core will be rapidly brought to substantially the temperature of the heater sheath 22 and hot water will be substantially instantaneously produced in the heater unit. It is to be understood that the outer shell ill of the heater will be suitably insulated so as to prevent loss of heat to the surrounding atmosphere.

From the foregoing description it will be observed that I have provided an improved liquid heater which is simple in construction, may be manufactured at relatively low cost, andls constructed and arranged so as to produce hot water substantially instantaneously upon the energize.- tion of the heater element located therein. It will also be observed that I have provided an electric heater constructed and arranged so that the liquid being heated passes through the heater in a substantially spiral path formed by the electric heater element, thus eflecting intimate contact between the heater element and liquid being heated so that 'efllcient heat transfer is obtained.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not intend to be limited thereto, since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I, claim as new and desire to secure by Letters Patent of the United States is:

1. In a liquid heater, an outer shell, an inner hermetically sealed hollow core member, and a spirally wound sheathed wire type of heating unit lying between the outer wall of said core memher; and the inner wall of said shell and cooperating therewith to define a spiral path through i said shell.

the spiral being substantially the same as the inside diameter of said outer shell and the inside diameter of the spiral being substantially the same as the outside diameter '01 said core member so as to define a. spiral path through said heater for the liquid to be heated;

3. In a. liquid heater, an outer shell, an inner hermetically sealed hollow metallic core memher, a heating unit lying between said outer shell and said core member, said heating unit being wound in the form of two spirals having snoutside diameter substantiallythe same as the-inside diameter of said outer shell, said outer shell and core member and heating unit cooperating to form a spiral path for the liquid being heated to follow in flowing through said heater.

4. In an electric hot water heater, an outer shell, an inner hermetically sealed hollow metallic core member, a spirally wound sheathed 'wire type of heating unit lying betweensaid outer shell and said core member, the said heating unit engaging the inside wall of said outer shell and the outside wall of said core member so as to define a spiral path through said shell for the liquid to be heated.

;5. In an electric liquid heater, an outer shell open at one end, a cap for closing said open end, means defining a liquid inlet and liquid outlet one of which is in said shell and the other in said cap, a hollow metallic cylinder arranged centrally within said shell, and a heating unit comprising a coiled resistance unit embedded in a mass of heat refractory electrical insulating material and encased by a metallic sheath spi= rally wound in the form of a double helix, said sheath of said heating unit engaging the outer wall of said cylinder and the inner wall of said shell to define a spiral path between said inlet and said outlet which the liquid being heated is adapted to follow.

6. In a liquid heater unit, an outer shell having one end open and the other end substantially closed, means defining a liquid outlet in said closed end, a cap closing said open end, means defining a liquid inlet in said cap, a hollow metallic core member arranged centrally of said shell, a sheathed wire type of heating unit spirally wound about said core member, said heating unit engaging the outer wall of said core member and the inner wall of said shell to define a spiral path to be followed by liquid traveling through said shell, and means for sup porting said heater unit on said cap.

7. In an electric liquid heater, an outer shell having one end open and the other end substantially closed, a cap closing the open end of said shell and having a liquid inlet therein, a hollow metallic core member arranged centrally of said shell, 9. sheathed wire type heating unit spirally wound in the iorm oi two spirals arranged about said core member, said heating unit engaging the outer wall of said core member and the inner wall oi said shell to define a spiral path through the liquid heater unit for the liquid to be heated, means for suspending said heating unit from said cap, and an outlet sleeve in the closed end of said shell, said outlet sleeve having a plurality of openings therein so that the flow of liquid will continue uninter rupted if said suspended heating unit should sag so as to overlie a portion of said outlet sleeve. CHARLES C. ABBOTT. 

